Meshes turn black after baking lightmap

I’ve been struggling to bake my scene for several days. And I don’t know where to look at to solve the issue.

I have a scene made up of some outdoor stuff and a room with no windows. Inside the room, there are four point lights. Models are imported OBJ models.
In the editor before baking, the everything looks nice. After the bake, things go black.

The upper half is what I expected, the lower half is what I got:

You can see the floor and walls are blacked out. And it seems light would go through the floor and light the basement below it.

In additional, I’ve turned off the skybox and directional light in this example, but when they were on, the light can shine through the walls.

Here is my light setting:

I am not familiar with 3D modelling, and don’t know what to do.
It would be appreciated if someone can point me to the direction of solving the issue.

Hi @aristojoyce

There could be several causes for this, one could be that you need to Generate Lightmap UVs. Try turn on “Generate Lightmaps UVs” in the import options of your meshes. Also, could the normals be flipped?